diff --git a/.github/workflows/tests.yaml b/.github/workflows/tests.yaml
index c9d58940aeb..912d62f98ee 100644
--- a/.github/workflows/tests.yaml
+++ b/.github/workflows/tests.yaml
@@ -21,22 +21,24 @@ jobs:
         standard: [20, 23]
         mode: [dev, debug, release]
         include:
-          # in addition to the above combinations, add a combination to build with
-          # dpdk. but only build this combination when dpdk is enabled, so we don't
-          # double the size of the test matrix, and can at least test the build
-          # with dpdk enabled.
+          # preserve the existing <clang++18, C++23, release> combination
+          - compiler: clang++-18
+            standard: 23
+            mode: release
+          # add "dpdk" to <clang++18, C++23, release>, so it builds with dpdk, as
+          # we don't want to double the size of the test matrix, and can at least
+          # test the build with dpdk enabled.
           - compiler: clang++-18
             standard: 23
             mode: release
             cooks: --cook dpdk
             enables: --enable-dpdk
-          # in addition to the above combinations, add a combination to build with
-          # C++20 modules. but only build this combination with C++20 modules enabled,
-          # so we don't double the size of the test matrix, and can at least test the
-          # build with C++20 modules enabled.
+          # add "--enable-cxx-modules" to <clang++18, C++23, release>, to build
+          # with C++20 modules, so we don't double the size of the test matrix,
+          # and can at least test the build with C++20 modules enabled.
           - compiler: clang++-18
             standard: 23
-            mode: debug
+            mode: release
             enables: --enable-cxx-modules
     steps:
       - uses: actions/checkout@v4